The Reason Why
by Lady Azura
Summary: What if there’s a deeper reason behind why Derek doesn’t want that feelgood family moment? Oneshot. Dasey.


Summary: _What if there's a deeper reason behind why Derek doesn't want that feel-good family moment? (One-shot. Dasey.)_

Disclaimer: Don't own _Life With Derek_. 'Nuff said.

Rating: T (For Derek's dirty mouth.)

Author's Note: I really don't know where this came from. It suddenly hit me just… completely out of the blue last night when I was thinking about all of Derek and Casey's "almost" hugs and wondering why Derek is so against them. I eventually came to THIS conclusion.

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**The Reason Why…****  
**_**By: Lady Azura**_

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"You didn't have to do that, you know."

Derek stiffened slightly at the sound of her voice, swinging around in his chair and slowly lowering the latest edition of _Sports Illustrated_ and staring blankly at the gorgeous (though he would never in a million years admit this to her face) brunette standing in his doorway with her arms folded across her chest.

It was almost 9:30 at night and despite the fact that she had stopped crying well over an hour ago, he could still make out some pinkness in her eyes. He looked away uncomfortably.

"I don't know what you're talking about," he muttered, "I didn't _do_ anything."

Casey bit her bottom lip, taking a few steps forward into his room and shutting the door behind her.

"I'm not an idiot, Derek." She said, "Sam and Em told me everything."

Derek rolled his eyes.

"Sam and Emily don't know jack about me or the reasons behind my actions." He spat, his eyes meeting hers. "Sam may be my best friend, but I don't tell him a lot."

Casey frowned.

"Derek, you nearly _killed_ Max. Sam and Ralph literally had to _pry_ you off of him so you wouldn't, and while I didn't see the whole thing, I _did_ see the end of your little fight." She said.

"He had it coming. We're rivals, after all. He's the Captain of the football team and I'm the Captain of the hockey team." Derek replied, shrugging.

Casey's brows furrowed and she planted her hands firmly on her hips.

"Who do you think you're talking to? I _know_ you're not stupid enough to try and _kill_ someone over some petty little rivalry. You prank rivals - you don't try to kill them or beat the living daylights out of them. I've known you long enough to know this much."

Derek scowled at her.

"You think you know _so_ much about me, Case, but the truth is… you don't. _No one_ does. Now, will you _kindly_ drop the subject and get the fuck out of my room?"

"Damn it, Derek!" Casey snapped, slamming her hands against his desk. "I'm so sick of this! For once in your life, be honest with me! Why did you do it? Why didn't you just let me keep thinking he was my Prince Charming? Why didn't you let me find out on my own and be publicly humiliated in front of the entire school? I mean, _you_ have no problem doing that, so why does it bother you so much when someone else tries to? Why -"

"SHUT UP! JUST _SHUT UP_!" Derek shouted, abruptly standing up and reaching across his desk to silence her with his hand.

After a minute or so, he let his arm fall limply at his side.

"Do you _really_ want to know why I tried to kill Max?" He asked. When Casey nodded, he continued. "Fine. I'll tell you - but only because I know you won't leave if I don't."

He took a deep breath and began.

"He cheated on you with his ex-girlfriend."

"I _know_ that."

"No, but… he _cheated_ on you! He had the nerve to actually _sleep_ with another girl while he was still with you! And not only that, but he also spread a shit load of rumors about how you and him apparently did some _stuff_ over the holiday and how you were an easy lay who only acted like an innocent goody-goody to deceive people. That's why all those guys have been checking you out for the past few weeks, and that's why some of the girls have been giving you the cold shoulder. Well, word eventually got around to the hockey team and that's how _I_ found out."

"Wait! People were spreading rumors about me and you didn't tell me?" Casey snapped.

Derek narrowed his eyes.

"I _just_ did, didn't I?" He asked, "I thought it would just blow over before you found out - like the Klutzilla and grade-grubber incidents. Or that Emily would tell you."

"So… you beat him up because he spread some rumors about me?" She asked, tilting her head to the side.

"No." He said, "I beat him up because he cheated on you and played you like a fool. _You_. He has absolutely no idea what he lost! Amy's one of the biggest sluts in the school and she has absolutely no personality or any redeeming qualities about her. _You_ on the other hand… you're my step-sister. That in itself makes you a hundred times better than her. You're an amazing person and - oh God. Are you _crying_?"

Casey sniffed, dabbing her eyes with the sleeve of her blouse.

"No." She lied.

"Good. Cause you know I don't do the crying thing." He said, before continuing, "So anyways… Max cheated on you and broke your heart… so I broke his nose. That's all there is to it. Now, _leave_."

"But -"

"Nope. I told you everything - now go."

"Derek -"

"Leave."

"I -"

"Why the hell are you still standing there? _Shoo_!"

"DEREK!"

"_WHAT_?"

"I just wanted to say…" Casey hesitated for a few seconds, before stepping forward, "I just wanted to say… thank you."

With that, she leaned over and attempted to wrap her arms around him, but Derek quickly sensed what she was trying to do and shoved her away.

"What are you doing?" He asked defensively.

"_Trying_ to hug you?" Casey replied as if it were the most obvious thing in the world.

"Why?"

"Because I think this calls for a feel-good family moment."

"Uh, how about no?"

"Why not?" She asked, leaning over again.

Once more, he pushed her away.

"Because!" He said, "I don't do feel-good family moments!"

"Yes you do!" Casey accused. "You hug Marti all the time! I've even seen you hug Lizzie and Edwin on occasion!"

"Marti is Marti. She has that right. And as for the tweens… _they_ initiated the hugs. Not me."

Casey pouted, folding her arms across her chest once more.

"Derek, it seems to me that you have no problem hugging anyone in this family or at school _except_ for me. Why?"

"Again with the _why's_?" He groaned. "I already answered your questions! Now get out!"

"Not until you answer me this one last question," said Casey. Her face suddenly fell. "Do I disgust you _that_ much that you don't even want to _touch_ me? Do you hate me that much that -"

_'Oh God.'_ He thought, gripping the edge of his desk and squeezing his eyes shut.

"I'm right, aren't I? Everything you just told me was a lie, wasn't it? Just to get me out of your room because apparently you can't stand to look at me and -"

"Casey!" He cried, "Just… leave."

_'Before I do something I'll regret.'_

"No!" Casey snapped defiantly. "Not until you give me a logical explanation as to _why_ you refuse to hug me!"

Derek's eyes snapped open.

"Fine." He said, straightening up and walking around his desk so that he was now face-to-face with her. "You _really_ want to know why I won't give into your stupid feel-good family moments?"

Casey nodded.

Derek's eyes darkened and leaned closer so that his lips were just centimeters away from hers. Casey took a step back, causing him to step forward once again. This continued until her back met the door, trapping her between it and her step-brother. Derek smirked, placing his hands on her shoulders and sliding a knee between her legs.

"Because," he replied, "If we _ever_ have that moment… that feel-good family moment… it would mean admitting we're family and I just _can't_ do that."

"Why not?" asked Casey, even though subconsciously, she had an idea as his hands slid from her shoulders to her hips.

"Because I fucking love you." He replied.

Before Casey could respond, Derek swooped down and pressed his lips against hers. Instinctively, Casey's eyes drooped shut and she wrapped her arms around his neck, pressing herself against him. All logic seemed to disappear, and during this fleeting moment, she completely forgot that she had _just_ broken up with her ex-boyfriend just hours before and that this was her _step-brother_ she was currently locking lips with. The same step-brother who tormented her on a daily basis and the same one she was supposed to despise. At that moment though… she just couldn't bring herself to care.

Derek smirked when he felt her fingers entangle themselves in his hair and slid one hand down to lift her knee and wrap it around his waist. An interesting noise escaped his lovely step-sister's lips and he quickly pulled away and pressed into her, watching her head fall back against the door and lull from side to side. Leaning forward once again, he began to plant nips and kisses on the side of her neck, taking great pleasure in the small moans that she would emit every time he reached a sensitive spot.

"Derek," she breathed after a few minutes.

He ignored her, continuing his path down her neck and pushing some fabric of her blouse away so that he could reach her shoulder.

"Derek, wait," she said again, this time in a more demanding - but still dazed - tone.

He reluctantly pulled away.

"What?" He asked.

"I just… stop that! It's distracting!" She snapped when he started suckling on the area where her neck and shoulder met.

He pulled away again.

"I just… did you really mean what you said before?" She asked.

"That depends. You're not going to make me say it again, are you?" He asked.

"Derek! This is serious!"

"I am serious!" He shot back. "You know I'm not good with the whole PDA thing. Or affection at all, for that matter."

She narrowed her eyes.

He sighed.

"Fine. This is the last time you'll hear me say it, though." He cleared his throat. "Casey McDonald… I love you. There! You happy now?"

"Oui." She replied, beaming at him. "But just so you know… we have _a lot_ to discuss tomorrow."

He rolled his eyes.

"Of course."

"Like how this relationship is going to work -"

"Uh-huh."

Casey smiled, leaning forward to peck him on the lips before gently pushing him away.

"Goodnight, Derek."

With that, she opened the door and exited the bedroom. Derek waited until he heard her own door click shut before closing his own.

"Goodnight, Casey."

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**Well… that was random.**

**So anyways. My theory about why Derek doesn't want that feel-good family moment with Casey?**

**Because he loves her, and if he gives into it… it would be like admitting that she IS family. You know?**

**So… yeah.**

_**-Lady Azura-**_


End file.
